MEMOIR OF DAXIEL TREADWELL. 



349 



l)i|)c open throughout its length, but its sides iieing pcri'ecfly tight, and iiaving the several 

 vertical flexures here represented; and let it he required lo pass water, or any heavy fluid, 

 through it in the direction A to B, the end A being elevated the distance ah above 13 ; cd 

 being a horizontal line. It is evident that the water, being let into the end at a, will pass and 

 lill the i)ii:)e to e, displacing all the air with wliieh the pipe, being open to the atmosphere, 

 was previously full. Flowing over the curvature e in a stream or cohnnn less than the base 

 of the pipe, it fills the curvature at / without displacing the air previously contained in the 

 descending section from e to/. This air is thus shut up, and cannot pass from the pipe in any 

 direction without passing under the water, which, from its inferior specific gravity, is im- 

 possible. The water, continuing to flow over the flexure c, rises from / to [/, and, flowing over 

 the flexure, the same thing is repeated as to the air from fj to h which took jilace at the flexures 

 e and /'; rising from /( until it reaches some point, * for example, at which the sum of the 



perpendicular heights of the ascending columns '•(•,/(/, etc. arc equal to the height of the 

 cohnnn a h. . . . That is, if we suppose the air to be unelastic and void of weight ; but as this is 

 not true in fact, the air will be condensed in a greater or less degree, according to its volume 

 and the height of the columns of water opposed to it. In consequence of this condensation, the 

 water will rise, as shown in the figure, to k and m, for cxam]:)le ; and the weight of these columns, 

 being added to the efl'ective force of the column a h, [iroduces a rise of the water to some jjoint ii 

 in the flexure h n. There is then a perfect equilibrium in the opposing forces, and the water can 

 flow no farther. 



"As the aqueduct at the Mill-dam was more or less bent through its whole course, the 

 flexures being considerable at the creeks under which it passed, it appeared to me certain that 

 it was partly filled with air, and that this alone interrupted the flow of water. On opening 

 small holes into it in several places, air rushed out in great quantity ; still, however, the water 

 did not flow at the reservoir, and, as it was impossible to get at the bending in every part of 

 the pipe without the labor of uncovering it wholly, this design was abandoned. A forcing 

 pump was then coupled to the upper cud of the pipe, and water which had been heated in the 

 worm-tub of a distil-house in the vicinity, was forced into it. The pump was furnished with 

 a valve loaded with a weight equal to a column of water eighty feet Jiigh, and a very small 

 opening made into the reservoir at the mills, so that the water, passing slowly through the 

 whole length of the aqueduct, was there discharged. The object of this ajiparatus was to pro- 

 duce an absorption of the air, by bringing it in contact, under heavy pressun;, with water which 

 had parted with some of its air by being heated ; as these conditions arc known to be favorable 

 to the absorption of air by water. The ])umpiug was continued about ten days, and the 

 quantity of water may be taken at about twenty hogsheads. The pump was then taken off, 

 and the aqueduct o]icncd into the fountain. The water was now found to flow at the reservoirs, 

 discharging as much as was due to the head, and continued to flow uninterruptedly." * 



• Boston Juiinial nf I'liilosiiphy uiid the Arts, Vol. II. p. 4tK5. 



